Yet another birthday bash for Stephen Sondheim's 75th, this one from BBC Radio 3, entitled Perfect Relationships, which one might argue are found only in the words and music of Sondheim songs. A perfect example set the tone when the very talented Julian Ovenden sauntered to the piano and wistfully accompanied himself in the title number from Anyone Can Whistle. "What's hard is simple," he sang, "what's natural comes hard." In that painful truth and the aching melody, he laid bare the heart of what makes Sondheim special.

After more than half a century advancing the delicate art that is musical theatre, no one has turned expectation on its head as he has, or shown more tellingly how songs elevate drama, how "the play's the thing" but the musical is something else. Why people need to sing was reiterated time and again in a mighty handful of his songs, all pointing towards a concert performance of his breakthrough musical Company.

The level of performance was mixed, the lack of preparation time clearly compromising. Alison Jiear could have sharpened the laughs in "Could I Leave You?" (Follies) had the text really been second nature. But the spirit prevailed. Sondheim songs raise everyone's game, none more so than Kim Criswell. Her artistry showed in numbers like "In Buddy's Eyes" and "Send in the Clowns", the greatest song ever written about missed opportunity.

And then Company, to remind us just how far ahead of the game Sondheim was in 1970. It was a brand new musical that sounded brand new. It's still brand new, dazzling. Performance-wise, things took an upturn. Martin Yates and the BBC Concert Orchestra kept things tight - too tight for poor Melanie Marshall, for whom the nightmarish patter of "Getting Married" became, well, nightmarish.

But the wit and heartache of Company comes too fast to fret over dropped stitches. And there are the stand-out moments: Jiear singing "Another Hundred People", Criswell letting the vodka stingers do the talking in "The Ladies Who Lunch", and a stonking performance of "Being Alive" from Ovenden. Hear it all for yourself on Boxing Day at 7.30pm, BBC Radio 3.